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Quantum chemical Computational, molecular structure and pred

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soma moh

on 28 April 2014

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Transcript of Quantum chemical Computational, molecular structure and pred

The calculated quantum chemical parameters for

flavonoid derivatives
to determine the inhibition efficiency for steel and copper.

(highest occupied molecular orbital energy),

(lowest unoccupied molecularorbital energy), the energy gap(∆E), hardness(η), Softness(S), dipole moment(μ), electronaffinity(EA), ionization potential(IE), the absolute electronegativity(χ) and the fraction of electron transferred (N) have been studied.

Molecular dynamic simulation,
Quantum chemical calculations,
Steel and Copper,
Flavonoid derivatives ,
Inhibitors .

The energy gap ΔE between the HOMO and LUMO has calculated for

ΔE= ( E - E )
The gap energy
Which related to derivative

, So this compound is the greatest inhibitory effect .

Quantum chemical methods have already proven to be very useful in determining the molecular structure as well as elucidat-ing the electronic structure and reactivity [1]. Thus, it has become a common practice to carry out quantum chemical calculations in corrosion inhibition studies. The concept of assessing the efficiency of a corrosion inhibitor with the help of computational chemistry is to search for compounds with desired properties using chemical intuition and experience into a mathematically quantified and computerized form. Once a correlation between the structure and activity or property is found, any number of compounds, including those not yet synthesized, can be readily screened employing computational methodology [2] and a set of mathemat-ical equations which are capable of representing accurately the chemical phenomenon under study [3,4].

Quantum chemical Computational, molecular structure and predictive QSAR modeling of flavonoid derivatives for corrosion inhibition of (Steel-Copper).

The optimized geometry of the flavonoid derivatives as inhibitors
HyperChem, Release 7.5

Aim of the work
Computational Details
For quantum chemical calculations, the study was carried out using semi-emiperical with basis set AM1 method with commercially available quantum chemical software HyperChem, Release 7.5 [5].

The calculated quantum chemical parameters included the energy of the highest occupied molecular orbital (E ), the energy of the lowest unoccupied molecular orbital (E ), the energy gap (∆E), the total energy of the molecule (TE), the electronic energy of the molecule (EE) and the dipole moments (μ).

Inhibitor 1

Inhibitor 2
Inhibitor 3
Inhibitor 4


Quantum chemical parameters for the studied inhibitors.
The dipole moment (
μ in Debye
) is another important electronic parameter that results from non
uniform distribution of charges on the various atoms in the molecule. The high value of dipole
moment probably increases the adsorption between chemical compound and metal surface [6].

From quantum theoretical calculations
The energy of the highest occupied molecular orbital (E ),
The energy of the lowest unoccupied molecular orbital (E ).

Inhibitor 4
The frontier molecular orbital theory (
), the shapes and symmetries of the highest-occupied and lowest-unoccupied molecular orbitals (
) are crucial in predicting the reactivity of a species .
The highest occupied molecular orbital of the flavonoid inhibitors by using AM1 method.

The FMO revealed that the formation of a transition state is due to an interaction between frontier orbitals (HOMO and LUMO) of reacting species [7].
Frontier orbitals plots of flavonoid derivatives, the lowest unoccupied molecular orbital of the inhibitors by using AM1 method.

The plot confirms the findings that flavonoid derivatives is adsorbed on metal surface via Oxygen atoms on the molecules .
The number of electrons transferred (∆N) was also calculated depending on the quantum chemical method .

Values of ∆N showed that the inhibition effect resulted from electron donation. Compound (4) had the highest inhibition efficiency because it had the highest HOMO energy and lowest ∆N values, and it had the greatest ability of offering electrons .
The flavonoid derivatives can be inhibition of steel
( ∆N= 0.21 -0.26)
more than in the case of copper metal
( ∆N= 0.00119 - 0.00844)

Calculated Energy of the
flavonoid derivatives
by using AM1 level.

The binding ability of the inhibitor to the metal surface increases with increasing of the HOMO and decreasing of the LUMO energy values .
The Mulliken charges of the atoms for the compounds 3 and 4 ,the more negatively charged an hetero atom, is the more it can be adsorbed on the metal surface
through the donor - acceptor type reaction .

The map of electrostatic potential surfaces for the studied compounds (the electron rich region is red and the electron poor region is blue in the neutral molecules).
The Mulliken population analysis was studied for flavonoid which indicated the inhibitors can be adsorbed on the metal surface using these active centers (i.e.) O (Oxygen) from the hydroxy and methoxy groups .
The order of inhibition efficiency of the flavonoid derivatives was more inhibited compound in the case of steel rather than copper.

[1] J.M. Bastidas, P. Pinilla, E. Cano, J.L. Polo, S. Miguel, Corros. Sci., Copper corrosion inhibition by triphenylmethane derivatives in sulphuric acid media (2003) 45: 427-449
[2] N.O. Eddy, U.J. Ibok, E.E. Ebenso, A. El Nemr, H.E. El Ashry, J. Mol. Model., Quantum chemical study of the inhibition of the corrosion of mild steel in H2SO4 by some antibiotics (2009) 15:1085-1092
[3] T. Arslan, F. Kandemirli, E.E. Ebenso, I. Love, H. Alemu, Corros. Sci., Quantum chemical studies on the corrosion inhibition of some sulphonamides on mild steel in acidic medium (2009) 51: 35-47.
[4] R.G. Pearson, Proc. Nati. Acad. Sci., Absolute electronegativity and hardness correlated with molecular orbital theory (1986) 83:8440-8441
[5] M.J.S. Dewar, E.G. Zoebisch, E.F. Healy, J.J.P. Stewart, Development and use of quantum mechanical molecular models.76.AM1: a new general purpose quantum mechanical molecular model, J. Am. Chem. Soc. 107 (1985) 3902– 3909.
[6]. X. Li, S. Deng, H. Fu, T. Li, Electrochim. Acta. 2009, 54, 4089.
[7]. H. Wang, X. Wang, H. Wang, L. Wang and A. Liu, Jour. Molecular Modelling 13(2007) 147.

Done by
Somia Al-Elyani
Wala'a AL-Harbi
Bayan AL-Faifi
Atikh AL-Nhari
Dr. Hanaa Shokry

Depended on the value of energy gap, the trend for the variation of the inhibition efficiency follow the order
( 4 > 1 = 2 > 3 ).

Results and discussions
Full transcript